1. Field of the Invention
The present invention relates generally to user interfaces for computer systems and more specifically to displaying data that is private to a first user which cannot be seen by a second, collocated user.
2. Description of Related Art
In collocated, multi-user computer-based applications, two or more people use a single computer simultaneously in the same room. Although personal computers (PCs) easily support multiple simultaneous input devices (e.g., multiple joysticks or game pads), they do not easily support separate displays for each user. Currently, the only way to provide separate displays to different users in the same room is to provide a separate physical display to each user. This solution has two drawbacks. The first drawback is that providing separate displays for each user is more expensive than providing a single, interleaved display. The second drawback is that separate displays increase the psychological distance between the users. Instead of the users attending to the single display of a game or other application, each user attends to their own display, making it difficult, for example, for one user to understand what the other user is pointing at. The lack of support and high cost for private displays eliminates the widespread use of the class of collocated games or other applications where one user is shown private information that the other user should not see (for example, a user's hand of cards in a card game).
FIG. 1 shows a prior art display of an example collocated, multi-user computer-based game. In this example of a crossword-building game, the tiles 10 at the top of the figure belong to Player A, and the tiles 12 at the bottom belong to Player B. In a conventional computer display, both players see each other's tiles because the computer display 16 always shows the game board 14, Player A's tiles 10, and Player B's tiles 12. This ruins the game for the players. Similar outcomes occur in card games or other applications where one user needs to hide displayed information from another user. What is desired is a system having a single computer display which can, for example, show Player A only the public information such as game board 14 and Player A's private information, such as tiles 10, and can simultaneously show Player B only the public information and Player B's private information, such as tiles 12. More generally, a system having one computer display is desired whereby each one of multiple users can view information accessible to all users as well as private information accessible to only a single user. Such a system would be useful for collocated multi-user computer applications such as games or training exercises, as well as single user computer applications where the user desires privacy to exclude bystanders from obtaining the displayed information.